Abnormal cell proliferation is a characteristic symptom of cancer. Further, abnormal cell proliferation has been implicated in numerous other diseases (e.g., cardiovascular diseases, inflammatory diseases such as rheumatoid arthritis, diabetic retinopathy, etc.). Although many methods for treating or preventing aberrant cell proliferation have been developed, a significant problem with most existing therapies is selectively distinguishing between normal and abnormal cell proliferation.
Radiotherapy is one promising approach to selectively targeting abnormal cell proliferation. A number of different radiosensitizers have been described in the art and include thiols, nitroimidazoles and metal texaphyrin compounds (see, e.g., Rosenthal et al., Clin. Cancer Res., 1999, 739). Significant problems with existing radiosensitization approaches are (1) the formation of toxic byproducts derived from the radiosensitizers, which has limited their usefulness in cancer therapy; and (2) achieving sufficiently high density of free radicals to be efficacious under dose-limiting toxicity.
Another popular approach to selectively targeting abnormal cell proliferation is treatment with bioreductive compounds, which are selectively activated in a reducing environment. Since many cancers typically contain regions of low oxygen tension (i.e., hypoxia), compounds with low redox potentials (i.e., bioreductive compounds) may be selectively activated in the reducing environment of tumor cells without external activation.
Accordingly, new compounds are required to fully explore treating or preventing abnormal cell proliferation. These new compounds may have radiotherapeutic activity or bioreductive activity. Such compounds may be effective in treating or preventing various diseases associated with abnormal cell proliferation such as cancer without forming toxic byproducts.